What if you have a very well secured network infrastructure, and there is no way something bad like a sniffing can happen. In that case is there a need for turning on encryption?

Yes, as stated earlier this is a debatable topic and the best answer to this question will be “It depends”.

The best answer for this question is to understand the overhead of AES encryption (AES encryption is usually combined with padding) to the data transfer, and to analyze if there are any potential benefits by disabling it.

There might be some edge cases where in disabling encryption in a controlled fashion yielded benefits.

This definitely is food for thought, and I’m really interested to know your thoughts around this.